Substrate for ink jet head, ink jet head using the same, and manufacturing method thereof

ABSTRACT

The present invention provides a substrate for ink jet including a heating resistor generating thermal energy for discharging an ink from an ink discharge port and an upper protective layer which is formed above the heating resistor and has a contacting surface with the ink. Furthermore, the upper protective layer is made of an amorphous alloy consisting of Ta and Cr in which the content of Ta is more than that of Cr. This constitution allows for the substrate excellent in cavitation resistance and corrosion resistance, and capable of high durability while having similar discharge performance to that of a conventional protective layer made of a Ta film. The present invention further provides an ink jet head comprising the above-mentioned substrate, and a manufacturing method thereof.

TECHNICAL FIELD

The present invention relates to a substrate for an ink jet head whichdischarges a functional liquid such as an ink to a recording mediumincluding paper, plastic sheet, cloth, articles and the like; an ink jethead using the substrate; and a manufacturing method thereof.

BACKGROUND ART

As a general constitution of a head for use in ink jet recording, therecan be exemplified a constitution in which a plurality of dischargeports, ink flow paths connected to these discharge ports, and aplurality of electro-thermal conversion elements for generating thermalenergy used to jet an ink are provided. Each of the electro-thermalconversion elements has a heating resistor and an electrode forsupplying electric power to the heating resistor, and thiselectro-thermal conversion element is coated with an insulating film tosecure insulation between the respective electro-thermal conversionelements. Each ink flow path is connected to a common liquid chamber atan end opposite to the discharge port of the ink flow path, and in thecommon liquid chamber, the ink supplied from an ink tank as an inkreservoir part is reserved. The ink supplied to the common liquidchamber is led to the respective ink flow paths so that the ink is heldforming a meniscus in the vicinity of the discharge port. In this state,the electro-thermal conversion elements are selectively driven togenerate thermal energy, and the thus generated energy is then utilizedto rapidly heat the ink and to generate bubbles on a thermal actionsurface, so that the ink is discharged under a pressure caused by such astate change.

The thermal action part of the ink jet head during the ink dischargingtime is heated by the heating resistor and hence exposed to a hightemperature, and simultaneously, the thermal action part combinedlysuffers a cavitation impact due to the bubbling and contraction of theink, and a chemical action of the ink. This chemical action of the inkbrings about the following phenomenon. Specifically, color materials,additives and the like contained in the ink are heated at a hightemperature, whereby they are decomposed on a molecular level and changeinto hardly soluble substances, which are physically adsorbed on anupper protective layer. This phenomenon is called kogation. When thehardly soluble organic and inorganic substances are adsorbed on theupper protective layer in this way, thermal conduction from the heatingresistor to the ink becomes uneven, and in consequence, the bubblingbecomes unstable.

Heretofore, a Ta film which can relatively withstand the cavitationimpact and the chemical action of the ink has been formed so as to be athickness of 0.2 to 0.5 μm, whereby both of life and reliability of thehead has been intended.

Referring to FIG. 9, detailed description will be made about a conditioncaused by the bubbling and bubbling stop of the ink in the thermalaction part.

A curve (a) in FIG. 9 shows a change with time of surface temperaturesof the upper protective layer from a moment when a voltage is applied tothe heating resistor, in a case where a driving voltageV_(op)=1.3×V_(th) (V_(th) represents an ink bubbling threshold voltage),a driving frequency is set to 6 kHz and a pulse width is set to 5 μs.Furthermore, a curve (b) shows a growing state of formed bubbles from amoment when the voltage is applied to the heating resistor in a similarmanner. As shown by the curve (a), the rise of the temperature startsfrom the moment when the voltage is applied, and a temperature rise peakis observed slightly behind a predetermined pulse time (because the heatfrom the heating resistor slightly late reaches the upper protectivelayer). Afterward, the temperature mainly lowers due to thermaldiffusion. On the other hand, as shown by the curve (b), the growth ofthe bubble starts from a time when the temperature of the upperprotective layer reaches about 300° C., and after the maximum bubblingis reached, the bubbling stops. In the actual head, the above operationis repeated. In this way, the surface temperature of the upperprotective layer rises up to, for example, about 600° C. with thebubbling of the ink, which shows that ink jet recording is carried outwith the thermal action at the high temperature.

Accordingly, the upper protective layer which comes in contact with theink is required to have film properties excellent in heat resistance,mechanical properties, chemical stability, oxidation resistance, alkaliresistance and the like. As materials for use in the upper protectivelayer, in addition to the above-mentioned Ta film, noble metals,high-melting point transition metals, alloys of these metals, nitrides,borides, silicides or carbides of these metals, amorphous silicon or thelike are known in the prior art.

For example, as described in Japanese Patent Application Laid-Open No.2001-105596, an upper protective layer is formed on a heating resistorvia an insulating layer, in which the upper protective layer is made ofan amorphous alloy represented in a composition formulaTa_(α)Fe_(β)Ni_(γ)Cr_(δ) (wherein 10 at. %≦α≦30 at. %, α+β>80 at. %,α<β, δ>γ, and α+β+δ+γ=100 at. % are satisfied), and a contacting surfacethereof with the ink contains an oxide of the component substance, sothat a reliable recording head with a longer service life is proposed.

However, in recent years, the needs for higher quality of record imagesand higher performance such as high-speed recording in ink jet recordingapparatuses have been increased, and in order to meet the needs,enhanced ink performance has been required. For example, improvedcoloring properties and weather resistance have been demanded in orderto address the high-quality record images and also the prevention ofbleeding (blur between different color inks) has been demanded in orderto address the high-speed recording. Consequently, an attempt to addvarious components to the ink has been made. With regard to the kinds ofink, in addition to black, yellow, magenta, and cyan, a pale color inkobtained by reducing a concentration or the like has been developed,which has brought about diversification of the ink. In some case, thereoccurs a phenomenon that even the Ta film, which is conventionallyconsidered to be stable as an upper protective layer, corrodes due tothermochemical reaction with the ink. In the case where the inkcontaining a bivalent metal salt such as Ca and Mg or a componentforming a chelate complex is used, the above-mentioned phenomenonremarkably appears.

In order to further speed up the ink jet recording, driving by shorterpulse than ever (that is, driving with a driving frequency increased) isrequired. In such shorter pulse driving, since the process of heating,bubbling, bubbling stop and cooling in a thermal action part of a headis repeated in a short period of time, the thermal action part issubjected to a larger thermal stress in a shorter period of time ascompared to a conventional one. Furthermore, since the shorter pulsedriving concentrates cavitation impact arising from the ink bubbling andcontraction on an upper protective layer in a shorter period of timethan ever, an upper protective layer particularly excellent inmechanical impact property has been demanded.

While these various improvements in the ink have been advanced, aproblem has been found that in the case where an upper protective layerwith improved corrosion resistance to the ink as described above isformed, using a certain kind of ink may cause a product due to kogationto be remarkably deposited on a heating portion, thereby reducingdischarge performance.

Furthermore, as a manufacturing method of a substrate for ink jet withthe above-mentioned upper protective layer formed, a process by dryetching is generally used in many cases. However, in the case where theupper protective layer with improved corrosion resistance to the ink isformed, although high durability can be maintained for a long time, itis predicted that a process of forming a desired pattern or the like byetching or the like becomes difficult. FIGS. 8A to 8E illustrate it. Asshown in FIGS. 8A to 8E, in pattern formation of the upper protectivelayer, the process by dry etching generally used in many cases may causean insulating protective layer contacting the upper protective layer tobe etched. If etching selectivity between the insulating protectivelayer and the upper protective layer could be sufficiently secured as ina conventional substrate, it would be possible to etch the upperprotective layer with the insulating protective layer being left.Actually, over-etching at a boundary portion with the upper protectivelayer may produce a step (between A and B in FIG. 8E). Owing to such aphenomenon, the insulating protective layer becomes thinner at theboundary portion by etching so as to have a film thickness b smallerthan a designed film thickness b, which leads to insufficient exertionof a protective function thereof. Therefore, it is necessary to obtainconditions of control based on etching time in consideration of anetching rate of the upper protective layer by an etching gas to etchonly the upper protective layer and then to perform patter formation. Aproblem, however, has been found that since the upper protective layermay be left unetched or, on the contrary, the insulating protectivelayer may be etched due to unevenness attributed to devices or etchingconditions, the pattern formation of the upper protective layer may notbe performed stably.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide an ink jet headhaving a protective layer excellent in cavitation resistance andcorrosion resistance, and capable of high durability while havingdischarge performance similar to that of a conventional protective layermade of a Ta film.

It is another object of the present invention to provide a substrate foran ink jet head comprising a protective layer which has a long servicelife even if small dots corresponding to fine record images, high-speeddriving corresponding to high-speed recording or various kinds of inkare used, an ink jet head comprising the substrate, and a manufacturingmethod thereof.

It is a still another object to provide a substrate for ink jetincluding a heating resistor generating thermal energy for dischargingan ink from an ink discharge port, and an upper protective layerprovided above the heating resistor and having a contacting surface withthe ink, the upper protective layer being made of an amorphous alloyconsisting of Ta and Cr in which the content of Ta is more than that ofCr, an ink jet head comprising the substrate, and a manufacturing methodthereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentally cross-sectional view showing a substrate for anink jet head to which the present invention is applied.

FIGS. 2A, 2B, 2C, 2D, 2E, 2F, 2G and 2H are views illustrating a methodfor forming a jet element on the substrate for the ink jet head to whichthe present invention is applied.

FIG. 3 is an exemplary view showing a film forming apparatus for formingrespective layers of the substrate for the ink jet head to which thepresent invention is applied.

FIG. 4 is an exemplary view showing one constitutional example of an inkjet recording apparatus equipped with the ink jet head to which thepresent invention is applied.

FIGS. 5A, 5B, 5C and 5D are explanatory views illustrating the states ofburnt deposition and its separation in an upper protective layer.

FIGS. 6A, 6B and 6C are exemplary views showing cross-sections ofheating elements observed in a discharge durability test.

FIG. 7 is a graph showing an etching rate in relation to the content ofTa.

FIGS. 8A, 8B, 8C, 8D and 8E are views showing how the upper protectivelayer is subjected to dry etching.

FIG. 9 is a graph illustrating changes in temperature and a bubblingstate of the upper protective layer after applying a voltage.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is an exemplary fragmentally cross-sectional view showing asubstrate for the ink jet head to which the present invention may beapplied.

In FIG. 1, reference numeral 101 denotes a silicon substrate, referencenumeral 102 denotes a heat accumulating layer made of a thermal-oxidizedfilm. Reference numeral 103 denotes an interlayer film made of an SiOfilm, SiN film or the like which also has a function of accumulatingheat, reference numeral 104 denotes a heat resistive layer, referencenumeral 105 denotes a metal wiring layer serving as wiring made of ametallic material such as Al, Al—Si, and Al—Cu, reference numeral 106denotes a protective layer made of an SiO film, SiN film or the likewhich also serves as an insulating layer. Reference numeral 107 denotesan upper protective layer provided on the protective layer 106 forprotecting an electro-thermal conversion element from chemical andphysical impact arising from heating of the heating resistor.Furthermore, reference numeral 108 denotes a thermal action part inwhich heat generated in the heat resistive element of the heatingresistive layer 104 acts on ink.

The thermal action part in the ink jet head is a part which is exposedto high temperatures due to the heat generation in the heating resistorand mainly suffers cavitation impact arising from ink bubbling andbubbling contraction after bubbling or a chemical action of the ink. Thethermal action part, therefore, is provided with the upper protectivelayer 107 for protecting the electro-thermal conversion element fromthis cavitation impact or chemical action of the ink. This upperprotective layer 107 is subjected to dry etching by a chlorine gas orthe like after applying a mask of a predetermined pattern or wet etchingby hydrofluoric acid, boric acid, hydrochloric acid or the like afterapplying a resist of a predetermined pattern to be patterned.Thereafter, on the upper protective layer 107, a jet element providedwith a discharge port 110 for discharging the ink is formed using a flowpath forming member 109.

FIGS. 2A to 2H illustrate a method for forming the jet element of theink jet head, in which a liquid flow path and the discharge port areformed on the patterned upper protective layer 107.

As shown in FIG. 2A, an SiO₂ film 502 is formed with a thickness ofabout 2 μm on a lower surface of a substrate for an ink jet head 501(including the silicon substrate 101, the heat accumulating layer 102,the interlayer film 103, and the heating resistive layer 104, the metalwiring 105, the insulating protective layer 106 and the upper protectivelayer 107 subjected to predetermined patterning, respectively) under atemperature condition of 400° C. by CVD method. Here, reference numeral507 corresponds to the thermal action part 108.

As shown in FIG. 2B, a resist is applied on this SiO₂ film 502 to forman opening 511 by dry etching or wet etching after exposure anddevelopment. The SiO₂ film 502 will serve as a mask when a through-hole513 is formed later and the through-hole 513 will be formed from theopening 511. Etching of the SiO₂ film 502 is performed, for example, inthe case of dry etching, by reactive ion etching or plasma etching usingCF₄ as an etching gas, and in the case of wet etching, using bufferedhydrofluoric acid.

Next, as shown in FIG. 2C, a PSG (phosphosilicate glass) film 503 isformed with a thickness of about 20 μm on the upper surface side of thesubstrate under a temperature condition of 350° C. by CVD method.

Next, as shown in FIG. 2D, the PSG film 503 is processed to form apredetermined flow path pattern.

Here, it is preferable to process the PSG film by dry etching using aresist, as it does not damage the SiO₂ film 502 on the lower surface.

Next, as shown in FIG. 2E, a silicon nitride film 504 is formed with athickness of about 5 μm on the PSG film 503 formed in the flow pathpattern under a temperature condition of 400° C. by CVD method. At thistime, an opening 512 is also filled with the silicon nitride film.

Here, since the film thickness of the formed silicon nitride filmdefines a thickness of the discharge port and the film thickness of thePSG film formed previously defines a gap of the ink flow path, therebylargely affecting ink discharge properties of the ink jet, the filmthicknesses of the silicon nitride film and the PSG film are determinedaccording to the required properties.

Next, as shown in FIG. 2F, the through-hole 513 is formed on the siliconsubstrate 501 as an ink supply port by using the SiO₂ film as a mask,which has been shapened previously. Although any forming method of thethrough-hole can be used, ICP (inductively coupled plasma) etchingmethod with CF₄ and oxygen used as an etching gas is preferable becauseit does not electrically damage the substrate and it allows theformation at low temperature.

Next, as shown in FIG. 2G, a discharge port 514 is formed by dry etchingusing the silicon nitride film 504 as a resist. As this forming method,reactive ion etching, which is excellent at anisotropic etching, isused.

Next, as shown in FIG. 2H, the PSG film 503 is eluted and removed fromthe discharge port 514 and the through-hole 513 using bufferedhydrofluoric acid.

Thereafter, a water repellent film containing Si is formed on a surfaceof the discharge port by plasma polymerization and an ink supply member(not shown) is attached on the bottom side of the Si substrate 501 tocomplete the ink jet head.

In addition to dry processes for forming the flow path and the dischargeport on the substrate as described above, the following wet processesmay be used to manufacture an ink jet head.

On the substrate for the ink jet head 501 (including the siliconsubstrate 101, the heat accumulating layer 102, the interlayer film 103,and the heating resistive layer 104, the metal wiring 105, theinsulating protective layer 106 and the upper protective layer 107subjected to predetermined patterning, respectively) as shown in FIG.2A, a resist is applied as a soluble solid layer, which will become anink liquid flow path in the end, by spin coat method. The resist, madeof polymethyl isopropenyl keton, acts as a negative resist and ispatterned in a shape of the ink liquid flow path by using aphotolithography technique. Subsequently, a coating resin layer isformed to form the liquid flow path or the discharge port. Beforeforming this coating resin layer, a silane coupling treatment or thelike may be performed as required in order to improve adhesion. Thecoating film layer can be applied on the substrate for the ink jet headwith the ink liquid flow path pattern formed by a coating method whichcan be selected from well-known coating methods. Thereafter, an inkliquid supply port corresponding to 513 is formed from the back side ofthe substrate for the ink jet head by using anisotropic etching method,sand blast method, anisotropic plasma etching method or the like. Mostpreferably, chemical silicon anisotropic etching method usingtetramethyl hydroxylamine (TMAH), NaOH, KOH or the like may be used toform the ink liquid supply port. Subsequently, whole exposure by Deep-UVlight is performed to remove the soluble solid layer and thendevelopment and drying are performed.

In any process, the thermal action part of the ink jet head is a partwhich is exposed to high temperatures due to the heat generation in theheating resistor and mainly suffers cavitation impact arising from inkbubbling and contraction or a chemical action of the ink. Accordingly,the thermal action part is provided with the upper protective layer 107for protecting the electro-thermal conversion element from thiscavitation impact and the chemical action of the ink. The upperprotective layer 107 which comes in contact with the ink is required tohave film properties excellent in heat resistance, mechanicalproperties, chemical stability, oxidation resistance, alkali resistanceand the like. According to the present invention, there is formed anamorphous alloy consisting of Ta and Cr in which the content of Ta islarger than that of Cr. The amorphous alloy according to the presentinvention represents an alloy having an amorphous structure, whichexhibits no peak showing the presence of a specific crystal plane (or ifany, extremely low peaks) and a broad diffraction pattern in crystalstructure analysis by X-ray diffraction method.

Supposing the content of Cr in the amorphous alloy is represented by y,it is preferable that 0 at. %<y≦30 at. % is satisfied. Furthermore, itis more preferable that 0 at. %<y≦25 at. % is satisfied.

The film thickness of this upper protective layer 107 is selected from arange of 50 nm to 500 nm, preferably 100 nm to 300 nm.

Furthermore, the film stress of this upper protective layer has at leastcompression stress and is preferably not more than 1.0×10¹⁰ dyn/cm².

In the case where the above-mentioned upper protective layer 107 withimproved corrosion resistance is formed, since the surface thereof ishardly damaged because of high corrosion resistance, a product due tokogation tends to be generated easily, which decreases an ink dischargespeed or makes the jet itself unstable. It can be supposed that thereason why a smaller amount of kogation product is generated in a Tafilm used in a conventional protective layer 107 is that slightcorrosion and the kogation product are generated with balance in the Tafilm and the surface of the Ta film is scraped due to the slightcorrosion to inhibit the kogation product from being deposited.

However, as mentioned above, in the upper protective layer 107 to whichan SUS component is added to improve corrosion resistance, when a Tacomponent is increased to suppress the deposition of the kogationproduct, the durability cannot be improved. It can be supposed that thisis because an increase of the Ta component results in a decrease of theSUS component, which decreases a Cr component considered to contributeto the durability.

The upper protective layer 107 to which the present invention is appliedis amorphized by adding chemically stable Cr to the conventional Talayer and spots where crystal interfaces exist, which become startingpoints of corrosive reactions, are significantly reduced, therebyimproving the corrosion resistance as compared to the conventional Talayer.

Furthermore, since the upper protective layer 107 to which the presentinvention is applied has a composition of a high Ta content, the surfaceof the upper protective layer slightly corrodes to suppress thedeposition of the kogation product, which allows the same degree ofdischarge performance as that of the conventional Ta layer to bemaintained.

Here, referring to FIGS. 5A to 5D, differences between theconventionally used Ta layer and the TaCr film according to the presentinvention will be described.

FIG. 5A is an exemplary view showing the upper protective layer 107 andan interface with the ink in the case where the upper protective layer107 is made of the conventional Ta layer. A kogation product 301 isdeposited in the thermal action part by driving the heating resistor. Inaddition, Ta of the upper protective layer 107 makes up an oxidized film302 by heat generated during driving. The film thickness of thisoxidized film is increased as the number of driving pulses is increased,and the oxidized film is formed wholly in the film thickness directionin the end. Part of this oxidized film 302 is separated from the upperprotective layer 107 together with the deposited kogation product 301 asshown in FIG. 5B. It can be thought that in this way, the deposition ofthe kogation product 301 is suppressed to maintain the dischargeperformance and the film thickness of the upper protective layer 107 isreduced.

In contrast, as shown in FIG. 5C, in the upper protective layer 107 towhich the present invention is applied, the oxidized film 302 in theinterface with the ink is formed very thinly on a metal layer 303 ascompared to that of the conventional Ta layer. As shown in FIG. 5D, thisoxidized film 302 is separated from the upper protective layer 107together with the deposited kogation product 301 to suppress thedeposition of the kogation product 301, which allows the dischargeperformance to be maintained. At this time, since the oxidized film 302is formed very thinly as compared to that of the conventional Ta layer,a decrease in the film thickness of the upper protective layer 107 issmall, which supposedly improves the durability as compared to theconventional Ta layer.

Thus, the upper protective layer 107 is amorphized by adding chemicallystable Cr while having a proper content of Ta, which can improve thecorrosion resistance while maintaining the discharge performance.

Furthermore, since the upper protective layer 107 has a composition of ahigh Ta content, a reduction in the etching rate of the upper protectivelayer by a chlorine gas can be suppressed to be slight as compared tothe conventional Ta. Thereby, the etching quantity of the insulatingprotective layer is reduced and the reliability can be maintained.

The upper protective layer 107, which can be manufactured by variousfilm forming methods, generally, may be formed by magnetron sputteringmethod using a radio frequency (RF) power source or a direct current(DC) power source.

FIG. 3 shows an overview of a sputtering apparatus for forming an upperprotective layer.

In FIG. 3, reference numeral 4001 denotes two types of targetsconsisting of a Ta target and a Cr target. Reference numeral 4002denotes a flat magnet, reference numeral 4011 denotes a shutter forcontrolling film formation on a substrate, reference numeral 4003denotes a substrate holder, reference numeral 4004 denotes thesubstrate, reference numeral 4006 denotes a power source connected tothe target 4001 and the substrate holder 4003. Furthermore, in FIG. 3,reference numeral 4008 denotes an external heater provided in such amanner as to surround an outer peripheral wall of a film formationchamber 4009. The external heater 4008 is used to adjust the ambienttemperature of the film formation chamber 4009. An internal heater 4005for controlling the temperature of the substrate is provided on the backsurface of the substrate holder 4003. The temperature control of thesubstrate 4004 is preferably performed using both internal and externalheaters 4005 and 4008.

The film formation using the apparatus of FIG. 3 is performed asfollows. Firstly, air is evacuated from the film formation chamber 4009up to 1×10⁻⁵ to 1×10⁻⁶ Pa using an evacuating pump 4007. Next, an argongas is introduced from a gas introduction port 4010 to the filmformation chamber 4009 via a massflow controller (not shown). At thistime, the internal heater 4005 and the external heater 4008 are adjustedso as to obtain a predetermined substrate temperature and ambienttemperature. Then, power is applied to the target 4001 from the powersource 4006, and sputtering discharging is performed to form a thin filmon the substrate 4004 while adjusting the shutter 4011.

According to the present invention, the two types of targets, that isthe Ta target and the Cr target may be used to form a thin film bybinary simultaneous sputtering method in which power is applied from twopower sources connected to the respective targets. In this case, thepower applied to the respective targets may be controlled separately.Alternatively, a plurality of alloy targets whose compositions have beenadjusted in advance are prepared and each of the alloy targets issputtered separately or two alloy targets or more are sputteredsimultaneously to form a thin film with a desired composition.

Furthermore, as describe above, when the upper protective layer 107 isformed, the substrate is heated up to 100° C. to 300° C. to achievestrong film adhesion. In addition, by forming a film by sputteringmethod capable of forming particles having comparatively large kineticenergy as describe above, strong film adhesion can be achieved.

By making film stress have at least compression stress, and setting itto 1.0×10¹⁰ dyn/cm² or less, strong film adhesion can be achievedsimilarly. This film stress may be adjusted by setting the flow volumeof the argon gas introduced to the film forming apparatus, the powerapplied to the target, or the substrate heating temperature in eachcase.

The upper protective layer 107 made of the amorphous alloy filmaccording to the present invention is preferably applicable whether theprotective layer 106 provided under the upper protective layer 107 isthick or thin.

FIG. 4 is an outline view showing one example of an ink jet apparatus towhich the present invention may be applied. Incidentally, although theink jet apparatus shown in FIG. 4 is of an old type, the presentinvention applied to a latest ink jet apparatus brings about moreeffects.

A recording head 2200 is mounted on a carriage 2120 engaged with aspiral groove 2121 of a lead screw 2104 which rotates in conjunctionwith reciprocal rotation of a driving motor 2101 via driving forcetransmission gears 2102 and 2103. The recording head 2200 is movedreciprocally in arrow directions a and b along a guide 2119 togetherwith the carriage 2120. A paper pressing plate 2105 for recording paperP fed on a platen 2106 by a recording medium supply device (not shown)presses the recording paper to the platen 2106 across the movementdirection of the carriage 2120.

Reference numerals 2107 and 2108 denote photo-couplers which are homeposition detecting means for confirming the presence of a lever 2109 inthis region and switching the rotative direction of the driving motor2101. Reference numeral 2110 denotes a member supporting a cap member2111 for capping the entire recording head 2200, and reference numeral2112 denotes sucking means for sucking the inside of the cap member2111, by which suction recovery of the recording head 2200 is performedvia a cap opening 2113. Reference numeral 2114 denotes a cleaning blade,reference numeral 2115 denotes a moving member enabling this blade tomove in the anteroposterior direction. These are supported by a bodysupporting plate 2116. It is understood that as the cleaning blade 2114,a well-known cleaning blade as well as this embodiment can be applied tothis apparatus.

Furthermore, reference numeral 2117 denotes a lever for starting suctionfor suction recovery which moves with the movement of a cam 2118 engagedwith the carriage 2120, and thereby the movement of a driving force fromthe driving motor 2101 is controlled by publicly known transmissionmeans such as clutch changeover. A recording control unit (not shown)for sending a signal to a heating portion provided in the recording head2200 or controlling driving of the above-mentioned mechanisms isarranged on the side of a body of the recording apparatus.

The ink jet recording apparatus 2100 constituted as described aboveperforms recording with respect to the recording paper P fed on theplaten 2106 by the recording medium supply device while moving therecording head 2200 reciprocally across the entire width of therecording paper P, and since the recording head 2200 is manufactured inthe above-mentioned manner, the apparatus can achieve high-precision,high-speed recording.

Hereinafter, the present invention will be described in more detailreferring to film formation examples of the upper protective layer andexamples of the ink jet head using the upper protective layer made ofthis alloy film or the like. However, the present invention does not belimited by such examples.

Physical film properties were evaluated in the case where an amorphousalloy layer for use in the upper protective layer 107 according to thepresent invention was formed on a silicon wafer using the apparatusshown in FIG. 3 in the above-mentioned film forming methods.

Firstly, a thermal-oxidized film was formed on a monocrystal siliconwafer (substrate 4004), which was set on the substrate holder 4003 inthe film formation chamber 4009 of the apparatus shown in FIG. 3. Next,air was evacuated from the film formation chamber 4009 up to 8×10⁻⁶ Pausing the evacuating pump 4007. Thereafter, an argon gas was introducedfrom the gas introduction port 4010 to the film formation chamber 4009to set the following conditions inside of the film formation chamber4009.

Substrate temperature: 200° C.

Gas ambient temperature inside of the film formation chamber: 200° C.

Gas pressure inside of the film formation chamber: 0.3 Pa

Next, either of the Ta target or Cr target was selected in each time andpower applied to the respective targets was set as shown in Table 1 toobtain film formation examples 1 to 6. A Ta film was formed in the filmformation example 1, a crystallized TaCr film in the film formationexample 2, and TaCr films of amorphous structure in the film formationexamples 3 to 6, with a film thickness of 200 nm on the thermal oxidizedfilm of the silicon wafer.

Furthermore, the Ta target and a Ta₁₈Fe₆₁Cr₁₅Ni₆ target were used andpower applied to the respective targets were set as Table 1 to obtain afilm formation example 7 of amorphous structure. Furthermore, the Crtarget and the Ta₁₈Fe₆₁Cr₁₅Ni₆ target were used and power applied to therespective targets were set as Table 1 to obtain a film formationexample 8 of amorphous structure.

The above-mentioned obtained samples were subjected to RBS (Rutherfordback scattering) analysis for the purpose of composition analysis. Theresults are shown in Table 1.

Next, X-ray diffraction measurement was performed for the TaCr films ofthe upper protective layers formed on the silicon wafers as describedabove for the purpose of structural analysis. As a result, Ta₈₉Cr₁₁exhibited a sharp diffraction peak, while Ta₇₈Cr₂₂ exhibited no specificdiffraction peak, which showed the transition from crystalline structureto amorphous structure.

Next, the film stress of the respective samples was determined based onthe amounts of substrate deformation before and after film formation. Asa result, a tendency was observed that as Cr composition is higher, filmstress changed from compression stress to tensile stress, and filmadhesion was reduced. By making the film stress have at leastcompression stress and setting it to 1.0×10¹⁰ dyn/cm² or less, similarlystrong film adhesion could be obtained. TABLE 1 Film Power [W]composition Crystal Ta Cr Ta₁₈Fe₆₁Cr₁₅Ni₆ [at. %] structure Filmformation 600 — — Ta crystalline example 1 Film formation 700 80 —Ta₈₉Cr₁₁ crystalline example 2 Film formation 600 150 — Ta₇₈Cr₂₂amorphous example 3 Film formation 600 100 — Ta₇₄Cr₂₆ amorphous example4 Film formation 500 150 — Ta₇₀Cr₃₀ amorphous example 5 Film formation500 500 — Ta₄₀Cr₆₀ amorphous example 6 Film formation 100 — 600Ta₂₈Fe₅₂Cr₁₅Ni₅ amorphous example 7 Film formation — 100 800Ta₁₇Fe₅₄Cr₂₅Ni₄ amorphous example 8(Relation Between Constitution of Upper Protective Layer and Kogation)

EXAMPLE 1

As a sample substrate to be evaluated with respect to ink dischargeproperties according to the present invention, an Si substrate or an Sisubstrate with a driving IC embedded was used. In the case of the Sisubstrate, an SiO₂ heat accumulating layer 102 (refer to FIG. 1) with athickness of 1.8 μm was formed by thermal oxidization method, sputteringmethod, CVD method or the like, and in the case of the Si substrate withIC embedded, an SiO₂ heat accumulating layer was formed similarly in themanufacturing process.

Next, an interlayer insulating film 103 made of SiO₂ with a thickness of1.2 μm was formed by sputtering method, CVD method or the like. Then, aheating resistor 104 represented in a composition formula of Ta₄₀Si₂₁N₃₉with a thickness of 50 nm was formed by reactive sputtering method usinga Ta—Si target. At this time, the substrate temperature was 200° C. AnAl film was formed with a thickness of 200 nm as metal wiring 105.

Next, patterning was performed using photolithography and a thermalaction part 108 of 30 μm×30 μm with the Al film removed was formed.Then, an insulator made of SiN with a thickness of 300 nm was formed asa protective layer 106 by plasma CVD method. Thereafter, Ta₇₈Cr₂₂ wasformed with a thickness of 230 nm as an upper protective layer 107 underthe conditions of the film formation example 3 shown in Table 1.Subsequently, the upper protective layer 107 was patterned by dryetching to manufacture a substrate for ink jet. In this case, it ispreferable to employ TaCr films produced in Examples 7 to 15 describedlater.

Furthermore, as described above, the upper protective layer 107 may bepatterned by wet etching using hydrofluoric acid instead of dry etchingto manufacture a substrate for an ink jet head.

Next, the ink jet head was manufactured using the substrate for ink jetmanufactured in either method. Then, discharge properties were evaluatedusing this ink jet head mounted on such an ink jet recording apparatusas shown in FIG. 4.

In this test, discharge speeds of the respective samples were measuredafter applying a driving signal of 1×10 ⁸ pulses with a pulse width setto 1 μsec at a driving frequency of 5 kHz. At this time, a drivingvoltage V_(op) was V_(th)×1.15. In addition, a commercially availableink for an ink jet printer (trade name: BCI-3e-Bk produced by CanonInc.) was used. V_(th) represents a bubbling threshold voltage at whichthe ink is discharged.

In Example 1, although the discharge speed was measured after applyingthe driving signal of 1×10⁸ pulses, no sufficiently major decrease couldbe observed to affect ink discharge properties. Furthermore, byobserving the surface of the heating resistor after evaluation, slightadhesion of a kogation product was confirmed.

EXAMPLES 2 AND 3

TaCr films having different compositions were formed with a thickness of230 nm using a similar method to that of Example 1 to be evaluated withrespect to ink discharge properties. The results are shown in Table 2.

COMPARATIVE EXAMPLES 1 TO 3

Ink discharge properties were evaluated using a similar method to thatof Example 1. As comparative examples, a Ta film, a Ta₄₀Cr₆₀ film, and aTa₂₈Fe₅₂Cr₁₅Ni₅ film each having a thickness of 230 nm were evaluated.The results are shown in Table 2. TABLE 2 Film composition Crystal JetKogation [at. %] structure speed product Example 1 Ta₇₈Cr₂₂ amorphousgood slight amount Example 2 Ta₇₄Cr₂₆ amorphous good slight amountExample 3 Ta₇₀Cr₃₀ amorphous good slight amount Comp. Ta crystallinegood small amount Example 1 Comp. Ta₄₀Cr₆₀ amorphous not good, largeamount Example 2 not bad Comp. Ta₂₈Fe₅₂Cr₁₅Ni₅ amorphous bad largeamount Example 3

As shown in Table 2, in the TaCr films of Examples 1 to 3 and the Tafilm of Comparative Example 1, the discharge speeds were maintainedafter applying the driving signal of 1×10⁸ pulses. In contrast, inComparative Examples 2 and 3, the discharge speeds were reduced so thatdesired recording image quality could not be maintained. The ink jetheads used for this jet property evaluation were disassembled to observethe generation of the kogation product at the thermal action partsthereof. As a result, in Comparative Examples 2 and 3, in which thedischarge speeds were largely reduced, a large amount of kogationproduct was observed to be deposited on the thermal action parts.Thereby, it was confirmed that the reduction in the discharge speed ofthe ink jet head was attributed to the deposition of the kogationproduct. This showed that as the content of Ta was decreased, thedeposition of the kogation product became remarkable, which preventedthe discharge properties from being maintained.

EXAMPLE 4

A discharge durability test was conducted using a similar ink jet headto that of Example 1. In this test, service life was detected when thejet was continued at a driving frequency of 5 kHz with a pulse width setto 1 μsec until the ink jet recording head was disabled to jet ink. Atthis time, the driving voltage V_(op) was V_(th)×1.15. In addition, anink containing about 4% of a bivalent metal with a nitric acid group,Ca(NO₃)₂.4H₂O was used. The results are shown in Table 3.

As shown in Table 3, even when the driving signal was continuouslyapplied up to 1.0×10⁹ pulses to continuously jet the ink, stable jet waspossible.

EXAMPLES 5 AND 6

Ink jet heads were prepared in a similar method to that of Example 4except that a Ta₇₄Cr₂₆ film (in Example 5) and a Ta₇₀Cr₃₀ film (inExample 6) were formed as the upper protective layers 107, respectively.Jet proof-tests were conducted in a similar method to that of Example 4using these ink jet heads. The results are shown in Table 3.

COMPARATIVE EXAMPLES 4 AND 5

Ink jet heads were prepared in a similar method to that of Example 4except that a Ta film (in Comparative Example 4) and a Ta₈₉Cr₁₁ film (inComparative Example 5) were formed as the upper protective layers 107,respectively. Jet proof-tests were conducted in a similar method to thatof Example 4 using these ink jet heads. The results are shown in Table3.

As shown in Table 3, in Comparative Examples 4 and 5, breaking occurredbefore reaching the application of a driving signal of 4×10⁸ pulses sothat the jet was disabled.

The above-mentioned results showed the following. As shown in theresults of Table 3, it was found that durability shown in the dischargedurability tests clearly depended on its crystal structure and a changeinto amorphous structure increased the durability. TABLE 3 Filmcomposition Crystal Pulse number of [at. %] structure normal jet Example4 Ta₇₈Cr₂₂ amorphous 1.0 × 10⁹ pulses or more Example 5 Ta₇₄Cr₂₆amorphous 1.0 × 10⁹ pulses or more Example 6 Ta₇₀Cr₃₀ amorphous 1.0 ×10⁹ pulses or more Comparative Tr crystalline 4.0 × 10⁸ pulses Example 4or less Comparative Ta₈₉Cr₁₁ crystalline 4.0 × 10⁸ pulses Example 5 orless

For an heating resistor of the ink jet head of Example 4, in which thedischarge durability test was conducted until the driving signal of1×10⁹ pulses was applied and an unbroken heating resistor of the ink jethead of Comparative Example 4, in which the discharge durability testwas conducted until part of a plurality of heating resistors werebroken, cross-sectional observation was conducted. Their exemplary viewswere shown in FIGS. 6A to 6C. Here, FIG. 6A shows an initial state ofExample 4 and Comparative Example 4, and reference numeral 401 denotes alayer corresponding to the upper protective layer 107 which is theTa₇₈Cr₂₂ film in Example 4 and the Ta film in Comparative Example 4.Furthermore, the reference numeral 108 denotes the thermal action part,the reference numeral 106 denotes the insulating protective layer, thereference numeral 105 denotes the metal wiring, and the referencenumeral 104 denotes the heating resistive layer. FIG. 6B is an exemplarycross-sectional view after the discharge durability test was conducteduntil the driving signal of 1.0×10⁹ pulses was applied to the heatingresistor of the ink jet head of Example 4, and reference numeral 402denotes an oxidized film formed on the upper protective layer 107. FIG.6C is an exemplary cross-sectional view of the unbroken heating resistorwhen the part of the heating resistors of the ink jet head ofComparative Example 4 were broken before reaching the application of thedriving signal of 4×10⁸ pulses, and reference numeral 403 denotes anoxidized film formed on the upper protective layer 107.

From these results, in Comparative Example 4, it was observed that mostof Ta on the thermal action part was oxidized as shown in the oxidizedfilm 403 and there existed regions which were locally depressed deeplyin the oxidized film. It can be supposed that in the broken heatingresistor of Comparative Example 4, this corrosion reached the heatingresistive layer 104, which caused breaking.

In contrast, in Example 4, the extremely thin oxidized film 402 wasformed on the upper protective layer 107 (401) on the thermal action108. The thickness was about 10 nm. Although the entire film thicknesswas slightly decreased to about 190 nm, most of the film remained in ametal state. As a result, it can be supposed that favorable dischargeproperties were maintained while maintaining durability in spite of thegeneration of the kogation product by a structure in which such anoxidized film 402 was formed.

As described above, according to Examples 1 to 6, in an ink jet head inwhich a kogation product was generated on an upper protective layerhaving an contacting surface with an ink by driving of a heatingresistor, by forming the upper protective layer made of an amorphousalloy consisting of Ta and Cr in which the content of Ta is more thanthat of Cr, it became possible to provide an ink jet head excellent incavitation resistance and corrosion resistance, and capable of highdurability while having discharge performance similar to that of aconventional protective layer made of a Ta film.

(2) Relation Between Constitution of Upper Protective Layer and Etching

Next, the fact will be described below that in the case where the upperprotective layer of the substrate for ink jet used in theabove-mentioned experiments is formed and patterned by dry etching, theupper protective layer to which the present invention is applied bringsabout an exceptional effect.

Firstly, there were prepared samples in which photoresists werepatterned in a predetermined shape on the metal films with respectivecompositions using the films according to the film formation examples 1to 8, and dry etching was performed to the respective samples at a powerof 300 W while introducing a Cl₂ gas at a flow of 100 sccm at a pressureof 1 Pa using a reactive ion etching apparatus. The results are shown inFIG. 7.

FIG. 7 shows that in the case where the dry etching was performed usingthe Cl₂ gas, the etching rate depends on the content of Ta and isdecreased with a decrease of the content of Ta.

Although in this experiment, dry etching was performed using the Cl₂gas, a mixed gas of the Cl₂ gas and other gases or cases using othergases exhibited a similar tendency.

Using the substrates for ink jet manufactured in such a manner,reliability was evaluated as described below.

EXAMPLE 7

A reliability test was conducted in order to evaluate reliability of theprotective layer after the upper protective layer 107 was subjected todry etching.

FIGS. 8A to 8E are exemplary cross-sectional views of a substrate forink jet. Here, the reference numeral 106 denotes the insulatingprotective layer, the reference numeral 107 denotes the upper protectivelayer, reference numeral 521 denotes a heater substrate including thesilicon substrate 101, the heat accumulating layer 102, the interlayerfilm 103, the heating resistive layer 104, and the metal wiring 105.Reference numeral 522 abstractly illustrates the thermal part 108 formedof the heating resistor layer 104 and the metal wiring 105 with such aconstitution as shown in FIG. 1. Furthermore, reference numeral 523denotes a resist.

In this test, it is evaluated whether or not the coverage by theinsulating protective layer is insufficient by etching up to theinsulating protective layer under the upper protective layer (a part Bin FIG. 8E). For this evaluation, the substrate for ink jet was immersedin a BHF (buffered hydrofluoric acid) solution for 20 minutes, andfurther immersed in a 3% NaOH (sodium hydroxide) solution for 10minutes. Etching conditions were set on the basis of an etching rate setin advance so that 20% over-etching might be performed. With respect toExample 7, it was observed whether or not erosion was developing fromthe part where the insulating protective layer was etched (the part B inFIG. 8E). As a result, from the fact that no part where the erosion wasdeveloping was found, it was confirmed that the reliability of theprotective layer was maintained.

EXAMPLES 8 TO 12

The reliability tests were conducted with respect to TaCr films withdifferent compositions in a similar method to that of Example 7. Theresults are shown in Table 4.

COMPARATIVE EXAMPLES 6 TO 9

The reliability tests were conducted in a similar method to that ofExample 7. As comparative examples, a Ta film, a Ta₄₀Cr₆₀ film, aTa₂₈Fe₅₂Cr₁₅Ni₅ film, and a Ta₁₇Fe₅₄Cr₂₅Ni₄ film were evaluated. Theresults are shown in Table 4. TABLE 4 Immersion Film Insulating Filmtest in BHF composition protective thickness and 3% NaOH [at. %] layer[nm] solutions Example 7 Ta₇₈Cr₂₂ SiN 230 good Example 8 Ta₈₉Cr₁₁ SiN230 good Example 9 Ta₇₄Cr₂₆ SiN 230 good Example 10 Ta₇₀Cr₃₀ SiN 230good Example 11 Ta₅₅Cr₄₅ SiN 230 not good, not bad Example 12 Ta₅₅Cr₄₅SiN 150 good Comp. Ta SiN 230 good Example 6 Comp. Ta₄₀Cr₆₀ SiN 230 badExample 7 Comp. Ta₂₈Fe₅₂Cr₁₅Ni₅ SiN 230 bad Example 8 Comp.Ta₁₇Fe₅₄Cr₂₅Ni₄ SiN 230 bad Example 9

As shown in Table 4, in Comparative Examples 7 to 9, a number oferosions of the wiring layer were observed in the part B of FIG. 8Esince etching invaded the insulating protective layer. In contrast, inExamples 7 to 10 and Comparative Example 6, erosions were not observed,which showed the reliability of the insulating protective layer wasmaintained. Furthermore, in Example 11, a few erosions were observed dueto a decrease of the etching rate, while in such a case as Example 12,in which the film thickness was thin, the etching quantity of theinsulating protective layer was decreased since the etching time wasdecreased, and no corrosion was observed in the reliability test.

These results showed that since the etching rate was decreased with adecrease of the content of Ta, the etching advanced up to the protectivelayer, which made the coverage insufficient.

EXAMPLES 13 TO 15

Similar reliability tests to that of Table 3 were conducted usingsimilar substrates for ink jet to those of Examples 9 to 11 except thatSiO was used for the protective layer 106. The results are shown inTable 5.

COMPARATIVE EXAMPLE 10

A similar reliability test to that of Table 4 was conducted using asimilar substrate for ink jet to those of Examples 13 to 15 except thatTa₁₇Fe₅₄Cr₂₅Ni₄ was used for the upper protective layer. The results areshown in Table 5. TABLE 5 Immersion Film Insulating Film test in BHFcomposition protective thickness and 3% NaOH [at. %] layer [nm]solutions Example 13 Ta₇₄Cr₂₆ SiO 230 good Example 14 Ta₇₀Cr₃₀ SiO 230good Example 15 Ta₅₅Cr₄₅ SiO 230 good Comp. Ta₁₇Fe₅₄Cr₂₅Ni₄ SiO 230 badExample 10

As shown in Table 5, in Examples 13 to 15, no corroded part wasobserved. This is because since the etching rate of SiO is lower thanthat of SiN and the protective layer 106 is made of SiO, the coverage ofthe protective layer is maintained. In contract, In Comparative Example10, a number of corrosions were observed.

Although the reliability of the insulating protective layer can bemaintained even in a region having a low content of Ta by making theTaCr film thinner or by selectively changing a base material to a properone, it is preferable that the content of Cr is 30 at. % or less inorder to strike a balance between the durability and the reliability ofthe insulating protective layer.

As described above, according to the above-mentioned Examples 7 to 15,in a substrate for an ink jet head having an insulating protective layerprovided on a heating resistor and an upper protective layer formed onthe insulating protective layer and patterned by dry etching, by formingthe upper protective layer made of an alloy consisting of Ta and Cr inwhich the content of Ta is more than the content of Cr, the protectiveability of the insulating protective layer in contact with the upperprotective layer can be inhibited from being reduced even if the upperprotective layer is patterned by dry etching. As a result, it becomespossible to provide an ink jet head having a protective layer excellentin cavitation resistance and corrosion resistance, and capable of highdurability. In particular, by embodying the ink jet head together withthe constitutions described in Examples 1 to 15, higher cavitationresistance, corrosion resistance, and durability can be achieved.

1. A substrate for an ink jet head comprising: a heating resistorgenerating thermal energy for discharging an ink from an ink dischargeport; an insulating protective layer provided above the heatingresistor; and an upper protective layer which is formed above theinsulating protective layer and patterned by dry etching and which has acontacting surface with the ink, the upper protective layer being madeof an amorphous alloy consisting of Ta and Cr, the content of Ta beingmore than the content of Cr.
 2. The substrate for the ink jet headaccording to claim 1, wherein the content of Cr of the upper protectivelayer is 30 at. % or less.
 3. The substrate for the ink jet headaccording to claim 1, wherein the film thickness of the upper protectivelayer is in a range of 50 nm to 500 nm.
 4. The substrate for the ink jethead according to claim 1, wherein the film stress of the upperprotective layer has at least compression stress and is 1.0×10¹⁰ dyn/cm²or less.
 5. An ink jet head comprising: a heating resistor generatingthermal energy for discharging an ink from an ink discharge port; and anupper protective layer which is formed above the heating resistor andhas a contacting surface with the ink, the upper protective layer beingmade of an amorphous alloy consisting of Ta and Cr, the content of Tabeing more than the content of Cr.
 6. The ink jet head according toclaim 5, wherein the upper protective layer is formed above aninsulating protective layer provided on the heating resistor, and ispatterned by dry etching.
 7. The ink jet head according to claim 5,wherein the content of Cr of the upper protective layer is 30 at. % orless.
 8. The ink jet head according to claim 5, wherein the filmthickness of the upper protective layer is in a range of 50 nm to 500nm.
 9. The ink jet head according to claim 5, wherein the film stress ofthe upper protective layer has at least compression stress and is1.0×10¹⁰ dyn/cm² or less.
 10. A recording unit for ink jet comprising:the ink jet head according to claim 5; and an ink reservoir partreserving an ink to be supplied to the ink jet head.
 11. The recordingunit for ink jet according to claim 10, wherein the recording unit forink jet has a cartridge form in which the ink jet head and the inkreservoir part are integrated.
 12. An ink jet apparatus comprising: theink jet head according to claim 5; and a carriage for moving the ink jethead along a recording surface of a recording medium.
 13. Amanufacturing method of a substrate for an ink jet head comprising: astep of forming a heating resistor on a substrate; a step of forming aninsulating protective layer on the heating resistor; and a step offorming an upper protective layer on the insulating protective layerfrom an amorphous alloy consisting of Ta and Cr in which the content ofTa is more than the content of Cr, and patterning the upper protectivelayer by dry etching.
 14. The manufacturing method according to claim13, wherein in the patterning step, the upper protective layer ispatterned by dry etching in which a chloride gas is used.